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Experimental Fuel-Cell Airplane's 2nd NASA Test
js7a writes "The Helios prototype, holding the sustained flight altitude record, having unsuccessfully completed its first test with a fuel cell, is almost ready for its first night flight this Thursday, Friday, or Saturday. Helios uses solar panels for flight with payloads over 600 lbs. planned for up to six months using regenerative electrolysis. What good is a plane that will fly for six months without refueling? Besides providing a UAV alternative to AWACS, they can improve internet connectivity."
surely gravity is less of an issue and the night-time drift downwards would be less significant
Wrong. Gravity still has about the same strength there as it does with your feet securely on the ground. The difference is only negligible. The only reason that satellites and other orbiting objects stay in space is because they are moving very quickly. Imagine this; An object traveling so fast that it is trying to leave earth orbit but it doesn't quite have enough energy to overcome the force of gravity and fly off into space. So it is constantly falling at the same rate, it's just balanced at the perfect position to not fly off and not to fall. This is called orbit. It's not because at some magic spot gravity ceases to be as effective. Look at the moon. Cheers!